Update to MSIX README.md (microsoft#1095)

* Update README.md

few adjustments

* Update README.md

* Update README.md

installer/README.md

@@ -7,14 +7,21 @@
   * The resulting installer will be built to `PowerToysSetup\bin\Release\PowerToysSetup.msi`.
 
 ## Building and installing self-signed PowerToys MSIX package
-For the first-time installation, you should generate a self-signed certificate and add it to the [TRCA store](https://docs.microsoft.com/en-us/windows-hardware/drivers/install/trusted-root-certification-authorities-certificate-store). That could be done by simply running ` 
-generate_self_sign_cert.ps1` from a powershell admin. After that:
+For the first-time installation, you'll need to generate a self-signed certificate.  The script below will generate and add a cert to your [TRCA store](https://docs.microsoft.com/en-us/windows-hardware/drivers/install/trusted-root-certification-authorities-certificate-store). 
+1. Open `Developer PowerShell for VS` as an Admin
+2. Navigate to your repo's `installer\MSIX`
+3. Run `.\generate_self_sign_cert.ps1`
 
-* Make sure you've built the `Release` configuration of `powertoys.sln`
-* Launch `msix_reinstall.ps1` from the devenv powershell
+## To Build
+1. Make sure you've built the `Release` configuration of `powertoys.sln`
+2. Open `Developer PowerShell for VS`
+3. Navigate to your repo's `installer\MSIX`
+4. Run `.\msix_reinstall.ps1` from the devenv powershell
 
+### What msix_reinstall.ps1 does
 `msix_reinstall.ps1` removes the current PowerToys installation, restarts explorer.exe (to update PowerRename shell extension), builds `PowerToys-x64.msix` package, signs it with a PowerToys_TemporaryKey.pfx, and finally installs it.
-## Removing all .msi/.msix PowerToys installations
+
+#### Removing all .msi/.msix PowerToys installations
 ```ps
 $name='PowerToys'
 Get-AppxPackage -Name $name | select -ExpandProperty "PackageFullName" | Remove-AppxPackage